Image reading and printing unit

ABSTRACT

An image reading and printing unit includes a carriage movable in a scan direction perpendicular to a transport direction of a sheet that is transported, a carriage moving part for moving the carriage in the scan direction, a platen arranged parallel to the scan direction with the transported sheet interposed between the platen and the carriage for cooperating a transfer of an image onto the sheet, a print head mounted on the carriage for printing the image on the sheet in a printing mode by moving from a receded position to a print position towards the sheet on the platen under the cooperation of the platen, an image sensor mounted on the carriage together with the print head for reading an image printed on the transported sheet in a reading mode, and a sensor moving part for moving the image sensor to make contact with the sheet on the platen in the reading mode so as to read the image printed on the sheet.

This application is a continuation of application Ser. No. 08/340,302,filed Nov. 14, 1994, now U.S. Pat. No. 5,635,973.

BACKGROUND OF THE INVENTION

The present invention generally relates to image reading and printingunits, and more particularly to an image reading and printing unit whichis mounted on a carriage of a serial printer and reads and printsimages.

Recently, proposals have been made to mount an image sensor on acarriage which moves a printing head of a serial printer, so as to carryout functions of an image scanner. In other words, the carriage printsan image on a sheet that is transported, and reads the printed document.Hence, there are demands to improve the quality of the reading withrespect to the transported document, and it is necessary to preventfocal error, change in magnification and the like caused by flapping orthe like of the transported document.

FIGS. 1A and 1B show the construction of a conceivable carriage mountedwith an image sensor. FIG. 1A is a plan view generally showing acarriage part of a serial printer, and FIG. 1B is a front view generallyshowing this carriage part.

A thermal serial printer 10 shown in FIGS. 1A and 1B includes a carriage11, and a thermal head 12 and an image sensor 13 which are mounted onthe carriage 11. In a case where a plain paper is used as the recordingsheet, a ribbon cassette 14 is also mounted on the carriage 11. Thisribbon cassette 14 accommodates a ribbon made up of a thermal transferfilm. The carriage 11 is moved in a scan direction A or B which isperpendicular to a transport direction of the sheet by a driving part 16under the guidance of a guide part 15. The recording sheet istransported at the time of printing, and the document is transported atthe time of reading. In addition, a platen 17 is arranged along the scandirection to confront the thermal head 12.

The image sensor 13 is provided on the side of the ribbon cassette 14and has an opening confronting the platen 17. The image sensor 13 ismade up of a compact optical system including a light source 18, a lens19 and a solid state image pickup (or reading) element 20 arranged on anoptical axis of the lens 19. The light source 18 and the lens 19 arearranged in a vicinity of the opening of the image sensor 13. In thiscase, the focal point of the image sensor 13 is adjusted by the lens 19to the sheet on the platen 17.

At the time of the printing, the thermal transfer film (ribbon) of theribbon cassette 14 is interposed between the recording sheet that istransported on the platen 17 and the thermal head 12 and is pushed bythe thermal head 12, so that ink of the thermal transfer film istransferred onto the recording sheet. On the other hand, at the time ofthe reading, the thermal head 12 is at a receded position with respectto the printed document that is transported, and the light source 18 ofthe image sensor 13 is turned ON so as to read the document by the solidstate image pickup element 20 as the carriage 11 moves.

Although not shown in FIGS. 1A and 1B, the sheet is transported in thisserial printer 10 by transport rollers which are arranged in a vicinityof a supply side relative to the platen 17. Generally, no transportmeans is arranged on an eject side relative to the platen 17.

However, a gap on the order of 1 mm, for example, is inevitably formedbetween the platen 17 and the image sensor 13. As a result, the flappingor the like of the document occurs with respect to the document that istransported within the range of this gap, and a focal error, a change inthe magnification or the like of the lens 19 are generated thereby. Forthis reason, there is a problem in that the quality of the readingdeteriorates because a stepped part occurs at a connecting partparticularly when reading an oblique line.

It is conceivable to increase the depth of field, however, the opticalpath will become long, and in this case, there is a problem in that thesize of the serial printer becomes large.

SUMMARY OF THE INVENTION

Accordingly, it is a general object of the present invention to providea novel and useful image reading and printing unit in which the problemsdescribed above are eliminated.

Another and more specific object of the present invention is to providean image reading and printing unit comprising a carriage movable in ascan direction perpendicular to a transport direction of a sheet that istransported, carriage moving means for moving the carriage in the scandirection, transfer means, arranged parallel to the scan direction withthe transported sheet interposed between the transfer means and thecarriage, for cooperating a transfer of an image onto the sheet,printing means, mounted on the carriage, for printing the image on thesheet in a printing mode by moving from a receded position to a printposition towards the sheet on the transfer means under the cooperationof the transfer means, image reading means, mounted on the carriagetogether with the printing means, for reading an image printed on thetransported sheet in a reading mode, and moving means for moving theimage reading means to make contact with the sheet on the transfer meansin the reading mode so as to read the image printed on the sheet.According to the image reading and printing unit of the presentinvention, it is possible to prevent focal error and change inmagnification of the image reading means that is formed by a compactoptical system. In addition, there is no need to increase the depth offield in order to prevent the focal error, and the quality of thereading can be improved while maintaining the reduced size of the imagereading and printing unit.

Other objects and further features of the present invention will beapparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B respectively are a plan view and a front view generallyshowing a conceivable carriage part of a serial printer;

FIGS. 2A and 2B respectively are a plan view and a front view generallyshowing an embodiment of an image reading and printing unit according tothe present invention;

FIG. 3 is a perspective view generally showing a carriage part of theembodiment;

FIG. 4 is a plan view for explaining a carriage movement;

FIG. 5 is a cross sectional view for explaining a sheet transport;

FIGS. 6A and 6B respectively are cross sectional views showing theconstruction of a sensor moving means; and

FIGS. 7A, 7B and 7C respectively are diagrams for explaining a cleaningmeans.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 2A and 2B respectively are a plan view and a front view generallyshowing an embodiment of an image reading and printing unit according tothe present invention. FIG. 3 is a perspective view generally showing acarriage part of this embodiment.

In FIGS. 2A, 2B and 3, an image reading and printing unit 21 of athermal serial printer includes a carriage 22, and a thermal head 23 andan image sensor 24 which are mounted on the carriage. The thermal head23 is provided as a printing means, and the image sensor 24 is providedas an image pickup (or reading) means. When a plain paper is used as arecording sheet, a ribbon cassette 25 is also mounted on the carriage22. This ribbon cassette 25 accommodates a thermal transfer film havingink as a transfer material.

The carriage 22 is moved in a scan direction A or B which isperpendicular to a transport direction of the sheet by a sheet transportmeans under the guidance of a guide part 26, as will be described laterin conjunction with FIG. 4. A platen 27 forming a transfer means isarranged along the scan direction to confront the thermal head 23. Thethermal head 23 is movable along the platen 27.

The sheet used is a recording sheet such as a plain paper or a thermalpaper at the time of the printing, and is a printed document at the timeof the reading. The sheet is transported between the thermal head 23 andthe platen 27 by the sheet transport means which will be described laterwith reference to FIG. 5.

A transparent glass member 24a shown in FIGS. 7A and 7B is formed on acontacting surface of the image sensor 24 making contact with thedocument. Alternatively, a slit 24c shown in FIG. 7C is formed in thecontacting surface of the image sensor 24 making contact with thedocument. The internal construction of the image sensor 24 is the sameas that of the image sensor 13 shown in FIG. 1A, and the image sensor 24includes a light source, a lens and a solid state image pickup element.For example, the image sensor 24 is provided on the left side of theribbon cassette 25.

A sensor moving means 28 for moving the image sensor 24 along the platen27 is provided within the carriage 22 and under the image sensor 24. Thesensor moving means 28 will be described later in conjunction with FIGS.6A and 6B. In this case, the required precision is obtained by an endsurface 22a of the carriage 22 and an end surface 24b of the imagesensor 24 which make contact with each other. Hence, the positionaldeviation of the image sensor 24 when it moves is restricted.

On the other hand, a white reference plate 29 for correcting a readingstate of the image sensor 24 is provided on one end of the plate 27 on ahome position side of the carriage 22. In addition, a cleaning means 30is provided in a vicinity of the white reference plate 29, so that thecleaning means 30 makes contact with or closely confronts the imagepickup surface of the image sensor 24 when the carriage 22 is at thehome position. The cleaning means 30 will be described later inconjunction with FIGS. 7A through 7C.

FIG. 4 is a plan view for explaining the movement of the carriage 22shown in FIGS. 2A, 2B and 3. In FIG. 4, a driving motor 31 is providedon one end of a moving range of the carriage 22, The driving motor 31rotates a pulley 31a, and is provided under the carriage 22 when viewedfrom the front. A timing belt 32 is provided across the pulley 31a and apulley 31b which is provided at the other end of the moving range of thecarriage 22. This timing belt 32 engages a lower part of the carriage22, and the carriage 22 is moved in the scan direction A or B under theguidance of the guide part 26. Hence, the driving motor 31, the pulleys31a and 31b, and the timing belt 32 form a carriage moving means.

FIG. 5 is a cross sectional view for explaining the sheet transport. Asupply roller 33 and pinch rollers 34a and 34b are provided in avicinity of the platen 27 and generally below the platen 27 when viewedfrom the side. The supply roller 33 and the pinch rollers 34a and 34bform the sheet transport means. A sheet 36 which may be the recordingsheet or the document is supplied from a sheet supplying part 35 of thethermal serial printer. The supplied sheet 36 is transported between theplaten 27 and the carriage 22 (and the thermal head 23) by the supplyroller 33 and the pinch rollers 34a and 34b. Of course, a plurality ofsupply rollers 33, a plurality of pinch rollers 34a and a plurality ofpinch rollers 34b may be provided along the platen 27.

FIGS. 6A and 6B respectively are cross sectional views showing theconstruction of the sensor moving means. FIG. 6A shows a cross sectionof the left side of the sensor moving means, and FIG. 6B shows a crosssection along a line C--C in FIG. 6A.

In FIGS. 6A and 6B, a holder 41 is integrally formed on the image sensor24. A support plate 22b is integrally formed on the carriage 22, and ashaft 42 which functions as a guide part is fixed across a side plate ofthe carriage 22 and the support plate 22b. The holder 41 movably engagesthis shaft 42. In this case, a coil spring 43 which urges the holder 41in a direction D is interposed between the support plate 22b and theholder 41.

The sensor moving means 28 is provided with a driving mechanism 44 forlinearly moving the image sensor 24 in the direction D or E using theshaft 42 as the guide. The image sensor 24 makes contact with thedocument 36 when moved in the direction D. The driving mechanism 44includes a motor 45 as its driving part, and this motor 45 can rotate inforward and reverse directions.

A worm gear 46 is fixed on a rotary shaft of the motor 45, and apartially toothed gear 47 engages this worm gear 46. This partiallytoothed gear 47 has gear teeth 47a provided only on a portion of itscircumference. The worm gear 46 and the partially toothed gear 47 form atransmitting part. A pin 48 is provided at an eccentric position of thepartially toothed gear 47, and this pin 48 engages an elongated hole 49in the holder 41. The elongated hole 49 extends in the directions D andE. A sponge 50 is provided in the elongated hole 49 as an urging member.Of course, a coil spring, a leaf spring, rubber and other resilientmembers may be used in place of the sponge 50 to form the urging member.

When the motor 45 rotates in the forward direction, the partiallytoothed gear 47 turns because the partially toothed gear 47 meshes withthe worm gear 46 for the span of the gear teeth 47a. As a result, thepin 48 on the partially toothed gear 47 moves linearly within theelongated hole 49 in the holder 41. Accordingly, the image sensor 24 ismoved in the direction D due to the driving force of the pin 48 and theurging force of the coil spring 43, and makes contact with the document36 that is transported on the platen 27. In this case, the pressure withwhich the contacting surface of the image sensor 24 makes contact withthe document 36 is determined by the urging force of the coil spring 43,and the pressure is 100 g to 150 g, for example.

In this state, an end of the gear teeth 47a of the partially toothedgear 47 is once disengaged from the worm gear 46. However, the pin 48pushes against the sponge 50 provided within the elongated hole 49, andthe restoration force (urging force) of the sponge 50 pushes the imagesensor 24 back in the direction E. As a result, the end of the gearteeth 47a of the partially toothed gear 47 and the worm gear 46 areengaged in the state where the image sensor 24 makes contact with thedocument 36.

Next, when the motor 45 is rotated in the reverse direction, the pin 48is moved linearly in the direction E due to the meshing of the worm gear46 and the gear teeth 47a of the partially toothed gear 47. Hence, thecontact between the image sensor 24 and the document 36 is released.

Therefore, the moving quantity (or distance) of the image sensor 24 inthe directions D and E is determined by the span or length of the gearteeth 47a of the partially toothed gear 47, and the image sensor 24 canbe positioned by rotating the motor 45 in the forward or reversedirection and stopping the motor 4. In other words, it is possible toposition the image sensor 24 along the directions D and E without havingto detect the position of the image sensor 24, and the image sensor 24can be fixed to a predetermined position by a simple operation ofcontrolling the motor 45 to rotate for a predetermined time and to stop.Of course, if the partially toothed gear 47 is not used, it is possibleto provide limit switches within the moving range of the image sensor 24for the purposes of detecting the position and restricting the movementof the image sensor 24.

The image sensor 24 makes contact with the document 36 only when readingthe document 36. The contact between the image sensor 24 and thedocument 36 is released at the time of the printing or when returningthe image sensor 24 to the home position after reading 1 line. Since theimage sensor 24 does not constantly make contact with the document 36,it is possible to prevent the sheet 36 (document or recording sheet)from being damaged by the contact. In addition, it is possible tosmoothly transport the sheet 36 when initially setting the sheet 36 inthe image reading and printing unit 21.

In this embodiment, the driving mechanism 44 is formed by the drivingpart (motor 45) and the transmitting part (worm gear 36, partiallytoothed gear 47 and pin 48). However, it is possible to realize thedriving mechanism 44 using a solenoid, an electromagnetic clutch and thelike.

FIGS. 7A through 7C are diagrams for explaining the cleaning means 30shown in FIGS. 2A and 2B. FIGS. 7A and 7B show cases where the glassmember 24a is provided at the contact surface of the image sensor 24,and FIG. 7C shows a case where the slit 24c is provided at thecontacting surface of the image sensor 24.

In FIG. 7A, the cleaning means 30 is arranged so that an end surfacethereof makes contact with the glass member 24a at the contactingsurface of the image sensor 24 when the image sensor 24 is located atthe home position. A cleaning member 51 is provided at this end surfaceof the cleaning means 30. For example, felt, gauze, brush and the likemay be used as the cleaning member 51. This cleaning member 51 removesdirt, dust particles, paper powder and the like that adhere on the glassmember 24a due to the contact between the image sensor 24 and the sheet36.

In FIG. 7B, the cleaning means 30 includes the cleaning member 51 and anair suction nozzle 52. The cleaning effect of the cleaning means 30 isimproved because the dirt, dust particles, paper powder and the likeadhered on the glass member 24a are wiped off by the cleaning member 51and any residual dirt, dust particles, paper powder and the like areremoved under suction by the air suction nozzle 52.

On the other hand, in FIG. 7C, the slit 24c is provided in thecontacting surface of the image sensor 24. Since dirt, dust particles,paper powder and the like are easily accumulated in the vicinity of theslit 24c, the air suction nozzle 52 is provided in a vicinity of theslit 24c so as to effectively clean the contacting surface of the imagesensor 24.

When carrying out the printing operation with respect to the recordingsheet 36 in the image reading and printing unit 21 described above, theimage sensor 24 is at the position receded in the direction E by thesensor moving means 28. With respect to the recording sheet 36 that istransported onto the platen 27 by the supply roller 33 and the like, thethermal head 23 is moved to push against the thermal transfer film ofthe ribbon cassette 25. The printing of one line is made from the leftend towards the direction B in FIG. 4, for example, and a predeterminednumber of lines can be printed in this manner.

Next, a description will be given of the reading operation of the imagereading and printing unit 21. When the carriage 22 is located at thehome position, that is, when the thermal head 23 is located at a printstartable position, the image sensor 24 is at the receded position andis in contact with the cleaning means 30 if the cleaning member 51 isused. The image sensor 24 is at the receded position and confronts thecleaning means 30 if only the air suction nozzle 52 is used. When thedocument 36 to be read is transported onto the platen 27, the carriage22 is moved in the direction B and is stopped at a position where thecontacting surface (for example, the glass member 24a) confronts thewhite reference plate 29. Then, the image sensor 24 is moved by thesensor moving means 28 in the direction D so as to make contact with thewhite reference plate 29.

In this state, the image sensor 24 makes a normal read operation byirradiating the light from the light source on the white reference plate29 and reading the reflected light via the lens and the solid stateimage pickup element. As a result, it is possible to detect the quantityof light (or light intensity) emitted from the light source, and achange in the light intensity during a settling time at the initialstart or caused by deterioration of the light source due to aging can bedetected. In other words, it is possible to store as a reference valuethe light intensity that is received when reading the white referenceplate 29 at the start of the read operation, and correct a set thresholdvalue of an output of the solid state image pickup element based on thestored reference value. As a result, it is possible to make a normal orcorrect read operation even when the light intensity changes for somereason, and a high resolution of 400 dpi or greater can be realized, forexample.

Thereafter, the carriage 22 is moved to a read start position, and thecontacting surface (for example, the glass member 24a) of the imagesensor 24 is pushed against the document 36. In addition, the carriage22 is moved in the scan direction A or B to read 1 line of the document36. Such a read operation is made for a predetermined number of lines ofthe document 36. In this case, it is possible to carry out the readoperation only when the carriage 22 moves in the direction B or, whenthe carriage 22 moves in both the directions A and B.

It is possible to bring the contacting surface of the image sensor 24 tothe position of the cleaning means 30 by moving the carriage 22 to thehome position every time one line is read along the scan direction B orevery time 2 lines are read along the scan directions B and A.

Accordingly, at the time of the reading, the document 36 is pushedagainst the platen 27 by the contacting surface of the image sensor 24,and the flapping or the like of the document 36 will not occur. For thisreason, it is possible to prevent focal error and change inmagnification of the image sensor 24 that is formed by the compactoptical system. In addition, there is no need to increase the depth offield in order to prevent the focal error, and the quality of thereading can be improved while maintaining the reduced size of the imagereading and printing unit 21.

On the other hand, because the contacting surface of the image sensor 24makes contact with or closely confronts the cleaning means 30 when thecarriage 22 returns to the home position, the maintenance of the imagereading and printing unit 21 becomes unnecessary for a long period oftime, and a stable read operation can be maintained for a long period oftime.

Further, the present invention is not limited to these embodiments, butvarious variations and modifications may be made without departing fromthe scope of the present invention.

What is claimed is:
 1. An image reading and printing unit for readingimages from and writing images to a sheet, comprising:a carriage movablein a scan direction; a sheet transport mechanism for moving the sheet ina direction perpendicular to the scan direction; a printing mechanismmounted on the carriage in a writing mode, for writing images to thesheet in the writing mode; a scanner mounted on the carriage in areading mode, the scanner having an imaging system for reading imagesfrom the sheet in the reading mode; and a scanner moving mechanism formoving the scanner into contact with the sheet in the reading mode andout of contact with the sheet in the writing mode.
 2. The image readingand printing unit as claimed in claim 1, wherein said printing mechanismincludes a thermal head.
 3. The image reading and printing unit asclaimed in claim 2, wherein said printing mechanism further includes athermal transfer film.
 4. The image reading and printing unit as claimedin claim 1, further comprising a reference plate provided at apredetermined position along the scan direction, said reference platebeing used for correcting a read state of said imaging system.
 5. Theimage reading and printing unit as claimed in claim 1, wherein saidscanner moving mechanism includes a guide part having said scannermovable provided thereon, and a driving mechanism linearly moving saidscanner towards the sheet under guidance of the guide part.
 6. The imagereading and printing unit as claimed in claim 5, wherein said scannermoving mechanism includes an urging member urging said scanner in adirection away from the sheet.
 7. The image reading and printing unit asclaimed in claim 1, wherein the printing mechanism moves toward thesheet in the writing mode and away from the sheet in the reading mode.8. The image reading and printing unit as claimed in claim 1,wherein thecarriage moves between first and second ends in the scan direction,wherein the scanner has a contact surface which contacts the sheet inthe reading mode, a transport member being provided in the contactsurface, and the unit further comprises a cleaner provided at the firstend of the scan direction to clean the transparent member when thecarriage is located at the first end.
 9. The image reading and printingunit as claimed in claim 8, wherein said cleaner includes a cleaningmember selected from the group consisting of felt, gauze and brush. 10.The image reading and printing unit as claimed in claim 9, wherein saidcleaner further includes an air suction nozzle cleaning the transparentmember of said scanner under suction.
 11. The image reading and printingunit as claimed in claim 1,wherein the carriage moves between first andsecond ends in the scan direction, wherein the scanner has a contactsurface which contacts the sheet in the reading mode, a slit beingprovided in the contact surface, and the unit further comprises acleaner provided at the first end of the scan direction to clean thecontact surface in the vicinity of the slit when the carriage is locatedat the first end.
 12. The image reading and printing unit as claimed inclaim 11, wherein said cleaner includes an air suction nozzle cleaningthe contact surface of said scanner, in the vicinity of the slit, undersuction.
 13. An image reading and moving unit for reading an image froma sheet, comprising:a carriage movable in a scan direction; a sheettransport mechanism for moving the sheet in a direction perpendicular tothe scan direction; a scanner mounted on the carriage, the scannerhaving an imaging system for reading an image from the sheet; and ascanner moving mechanism for moving the scanner into contact with thesheet in an activated mode and out of contact with the sheet in adeactivated mode.
 14. The image reading and moving unit as claimed inclaim 13,wherein the carriage moves between first and second ends in thescan direction, wherein the scanner has a contact surface which contactsthe sheet in the activated mode, a transparent member being provided inthe contact surface, and the unit further comprises a cleaner providedat the first end of the scan direction to clean the transparent memberwhen the carriage is located at the first end.
 15. The image reading andmoving unit as claimed in claim 14, wherein said cleaner includes acleaning member selected from the group consisting of felt, gauze andbrush.
 16. The image reading and moving unit as claimed in claim 15,wherein said cleaner further includes an air suction nozzle cleaning thetransparent member of said scanner under suction.
 17. The image readingand moving unit as claimed in claim 13,wherein the carriage movesbetween first and second ends in the scan direction, wherein the scannerhas a contact surface which contacts the sheet in the activated mode, aslit being provided in the contact surface, and the unit furthercomprising a cleaner provided at the first end of the scan direction toclean the contact surface in the vicinity of the slit when the carriageis located at the first end.
 18. The image reading and moving unit asclaimed in claim 17, wherein said cleaner includes an air suction nozzlecleaning the contact surface of said scanner, in the vicinity of theslit, under suction.
 19. The image reading and moving unit as claimed inclaim 13, further comprising a reference plate provided at apredetermined position along the scan direction, said reference platebeing used for correcting a read state of said scanner.
 20. The imagereading and moving unit as claimed in claim 13, wherein said scannermoving mechanism includes a guide part having said scanner movableprovided thereon, and a driving mechanism linearly moving said scannertowards the sheet under guidance of the guide part.
 21. The imagereading and moving unit as claimed in claim 20, wherein said scannermoving mechanism includes an urging member urging said scanner in adirection away from the sheet.